Federal Aviation Administration regulations require that an aircraft reciprocating engine shall not be returned to service after an annual or 100 hour inspection or overhaul unless the engine has first been tested in order to determine that certain operating characteristics fall within acceptable tolerances. Such characteristics include power output, magneto operation, fuel and oil pressure, and cylinder head and oil temperatures. Each must satisfy the manufacturer's recommendations before the engine can be returned to service and before the aircraft can be put back on the flight line. By way of illustration, Continental Aircraft Service Bulletin M81-5 requires that after major overhaul or cylinder replacement, each cylinder must be equipped with a temperature sensing device to monitor the head temperature. Likewise, Avco Lycoming Service Instruction 1427A states that engine revolutions per minute (RPM), oil temperature, cylinder head temperature, oil pressure and intake manifold pressure should be measured during ground run-in of a reciprocating aircraft engine following overhaul or replacement of a cylinder with new piston rings.
Current running-in procedures for an aircraft reciprocating engine are important, as they ensure the quality of engine repairs ranging from major overhaul to the replacement of a cylinder with new piston rings before returning the aircraft to the flight line. By monitoring certain operating parameters during engine run-in, various anomalies such as low oil pressure, high intake manifold vacuum, high oil and cylinder head temperatures, and improperly operating magnetos can be detected first on the ground, rather than in the air. Abnormal readings may be traced to underlying mechanical problems such as leaky oil filters, broken or inverted piston rings, improperly seated piston rings, clogged oil filters, coolant system leaks and the like before the aircraft is returned to service. Also, abnormal readings may be traced to underlying electrical problems such as faulty oil pump motors, defective spark plugs and other ignition-related problems.
Accordingly, it would be desirable to provide a self-contained, portable testing apparatus capable of monitoring such operating parameters to ensure that the requirements imposed by the FAA and the several aircraft engine manufacturers are fully satisfied.
Heretofore, various test rigs have required removal of the reciprocating engine from the aircraft in order to perform the run-in on a stationary engine test cell facility. This practice has proved very expensive and time consuming. Additionally, it poses the complication of transporting the engine to and from the stationary test cell facility. Predictably, the labor costs associated with transporting the engine from and to the aircraft and those incurred in detaching and reattaching the engine to the airframe after run-in testing are traditionally passed on to the consumer.
To facilitate conformance with required test procedures, several aircraft manufacturers have indicated that the aircraft is a suitable test stand for the running-in of aircraft reciprocating engines. For example, both Continental Service Bulletin M81-5 and Lycoming Service Instruction 1124B provide that run-in testing may be performed with the engine installed in the aircraft. But until now an inexpensive, portable, self-contained, independently powered apparatus has not been available to undertake this task.
In response to this need, the portable testing apparatus herein disclosed is used to monitor critical operating parameters of an aircraft reciprocating engine after the engine has been overhauled or after an annual, or other required inspection before it is returned to service.
A principal object of the invention is to provide a portable testing apparatus in order to simplify the running-in of reciprocating aircraft engines and to reduce the costs incurred in conducting run-in tests. The portable testing apparatus herein disclosed eliminates the transportation problems and the expense associated with running-in an engine at a stationary engine test cell facility by permitting the run-in test to be performed while the engine is attached to the airframe of the aircraft. Alternatively, the invention can be used conveniently to test an engine before mounting within the aircraft without having to transport the engine to a stationary test facility.